1. Field of the Invention
This invention relates to providing positive protection for station protectors, as provided at premises of telephone systems users. Positive protection means some arrangement for either preventing unauthorized removal of or interference with an arrestor in the protectors or which will indicate if removal of, or some interference with, an arrestor has occurred.
2. Related Art
Conventionally, a protector module or assembly has two arrestors, one for each line of a pair entering a customer's premises, i.e. Tip and Ring. The module usually has wells into each of which an arrestor is positioned, held in place by a hexagon headed screw cap screwed into the top of the well. A connection to ground is provided, and in use, on the occurrence of a overvoltage, there is a spark breakdown across a gap in an arrestor to the ground. Removal of the arrestor, without replacement, leaves the line unprotected against overvoltage surges and the like.
It has been proposed to arrange contacts in a well which are held apart by the presence of an arrestor. However, if the arrestor is removed then the contacts connect and short the line to ground. In this condition, the telephone service is non-operative. By putting a non-conductive member into the well, such as a short length of wood, and replacing the screw cap, the contacts are opened and service is restored. However, there is no protection. Thus the safety feature is readily overcome, without any indication that tampering has occurred.
Other arrangements also exist for attempting to prevent operation of the service with unprotected lines, but it is generally readily possible to circumvent the safety precautions.